Earth shaping vehicle retrofitted with rear grading tool

ABSTRACT

An earth shaping vehicle (ESV) includes a chassis and a rear earth shaping tool. The chassis drives the ESV through the site from a first location in the site to a second location in the site. The front earth shaping tool moves earth from the first location to the second location. The rear earth shaping tool grades a ground surface between first location and the second location. Sensors coupled to the rear excavation tool produce one or more signals representative of a position and an orientation of the rear tool relative to the ground surface of the site. A controller produces actuating signals to actuate the rear excavation tool to grade the ground surface based on the one or more signals representative of the position and the orientation of the rear tool.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/887,099, filed on Aug. 15, 2019, which is incorporated by reference in its entirety.

BACKGROUND Field of Art

The disclosure relates generally to a method for performing earth shaping operations, and more specifically to performing earth shaping operations using a vehicle configured with a rear grading tool.

Description of the Related Art

Vehicles, for example backhoes, loaders, and excavators, generally categorized as earth shaping vehicles, are used to excavate earth from locations. Currently, operation of these earth shaping vehicles is very expensive as each vehicle requires a manual operator be available and present during the entire operation. Further complicating the field, there is an insufficient labor force skilled enough to meet the demand for operating these vehicles. Because they must be operated manually, earth shaping operations can only be performed during the day, extending the duration of earth shaping projects and further increasing overall costs. The dependence of current earth shaping vehicles on manual operators increases the risk of human error during operations and reduce the quality of work done at the site.

Additionally, conventional earth shaping vehicles are outfitted with earth shaping tools which are not conducive for precise actuation movements or proprioception measurements. For example, conventional tractors are outfitted with an attachment tool mounted to the rear of the tractor, for example a ripper blade, which imprecisely and indiscriminately excavates earth by lowering the ripper blade beneath the ground surface and pulling the blade forward to excavate earth below the surface. Accordingly, there exists a need for a tractor outfitted with an attachment tool capable of performing earth shaping routines with increased precision.

SUMMARY

Described is an autonomous or semi-autonomous earth shaping system that unifies an earth shaping vehicle with a sensor system for moving earth within a site. The earth shaping system controls and navigates an earth shaping vehicle through an earth shaping routine of a site. The earth shaping system uses a combination of sensors integrated into the earth shaping vehicle to record the positions and orientations of the various components of the earth shaping vehicle and/or the conditions of the surrounding earth. Data recorded by the sensors may be aggregated or processed in various ways, for example, to determine and control the actuation of the vehicle's controls, to generate representations of the current state of the site, to perform measurements and generate analyses based on those measurements, and perform other tasks described herein.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an earth shaping system for moving earth, according to an embodiment.

FIG. 2 is a high-level block diagram illustrating physical components of an example off-unit computer, according to one embodiment.

FIG. 3 is a diagram of the architecture for an actuation assembly configured to actuate components of an earth shaping vehicle, according to an embodiment.

FIG. 4A illustrates a tractor outfitted with a front earth shaping tool and a rear ripper attachment, according to one embodiment.

FIG. 4B illustrates a tractor outfitted with a front attachment and a rear grading tool in place of a ripper attachment, according to one embodiment.

FIGS. 5A-C illustrate different views of a rear grading tool, according to an embodiment.

FIG. 6 is a system architecture diagram for controlling an earth shaping vehicle, according to an embodiment.

The figures depict various embodiments of the presented invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles described herein.

DETAILED DESCRIPTION I. Excavation System

FIG. 1 shows an earth shaping system 100 for excavating earth autonomously or semi-autonomously from a site using a suite of one or more sensors 170 mounted on an earth shaping vehicle 115 to record data describing the state of the earth shaping vehicle 115 and the site. As used herein, the term “autonomous” describes an earth shaping system enabled to actuate an earth shaping tool and navigate an earth shaping vehicle based on recorded sensor data.

The earth shaping system 100 includes a set of components physically coupled to the earth shaping vehicle 115. These components include an actuation assembly 110, the earth shaping vehicle 115 itself, a digital or analog electrical controller 150, an earth shaping tool 175, and an on-unit computer 120 a. In one embodiment, the actuation assembly 110 includes one or more of any of the following types of sensors: measurement sensors, spatial sensors, vision sensors, and localization sensors.

Each of these components will be discussed further below in the remaining sub-sections of FIG. 1. Although FIG. 1 illustrates only a single instance of most of the components of the earth shaping system 100, in practice more than one of each component may be present and additional or fewer components may be used different than those described herein.

I.A. Earth Shaping Vehicle

The earth shaping vehicle 115 is an item of heavy equipment designed to excavate earth from a hole within a site. Earth shaping vehicles 115 are typically large and capable of moving large volumes of earth at a single time, particularly relative to what an individual human can move by hand. As described herein, earth shaping refers generally to moving earth or materials within the site, for example to dig a hole, fill a hole, level a mound, or to deposit a volume of earth or materials from a first location to a second location. Materials, for example pieces of wood, metal, or concrete may be moved using a forklift, or other functionally similar machines.

In some embodiments, an earth shaping vehicle 115 is an excavation vehicle. Generally, excavation vehicles excavate earth by scraping or digging earth from beneath the ground surface. Examples of excavation vehicles within the scope of this description include, but are not limited to loaders such as backhoe loaders, track loaders, wheel loaders, skid steer loaders, scrapers, graders, tractors, bulldozers, compactors, excavators, mini-excavators, trenchers, skip loaders. In implementations involving excavation vehicles, the tool 175 is an earth shaping tool including not only an instrument collecting earth, such as a bucket or shovel, but also any articulated elements for positioning the instrument for the collection, measurement, and dumping of dirt. For example, in an excavator or loader the earth shaping tool refers not only to the bucket but also the multi-element arm that adjusts the position and orientation of the tool.

In addition to excavation vehicles, earth shaping vehicles may additionally refer to hauling vehicles, compacting vehicles, or any other vehicles deployed within a site to assist and optimize the performance of various earth shaping tasks. For example, an excavation vehicle may excavate earth from below the surface of a site and deposit the excavated earth into a hauling vehicle. The hauling vehicle transports the earth from a first location in the site to a second location (e.g., a fill location). At the fill location, the hauling vehicle fills the excavated earth into a hole and a compacting vehicle compacts the earth filled into the hole. In implementations for which multiple vehicles perform tasks, instructions are communicated to each vehicle in the site via the network 105.

More information regarding alternate earth shaping vehicles can be found in U.S. patent application Ser. No. 16/686,084, filed on Nov. 15, 2019, which is incorporated by reference herein in its entirety.

Among other components, earth shaping vehicles 115 generally include a chassis (not shown), a drive system (not shown), an earth shaping tool 175, an engine (not shown), an on-board actuation assembly 110, and a controller 150. The chassis is the frame upon on which all other components are physically mounted. The drive system enables the earth shaping vehicle 115 to move through the site. The earth shaping tool 175 includes not only the instrument collecting dirt, such as a bucket or shovel, but also any articulated elements for positioning the instrument for the collection, measurement, and dumping of dirt. For example, in an excavator or loader, the earth shaping tool refers to not only the bucket, but also to the multi-element arm that adjusts the position and orientation of the tool.

The engine powers both the drive system and the earth shaping tool 175. The engine may be an internal combustion engine, or an alternative power source, such as an electric motor or battery. In many earth shaping vehicles 115, the engine powers the drive system and the earth shaping tool through a single hydraulic system, however other means of actuation may also be used. A common property of hydraulic systems used within earth shaping vehicles 115 is that the hydraulic capacity of the vehicle 115 is shared between the drive system and the earth shaping tool 175. In some embodiments, the instructions and control logic for the earth shaping vehicle 115 to operate autonomously and semi-autonomously includes instructions relating to determinations about how to allocate the hydraulic capacity of the hydraulic system given circumstances in the site and the earth shaping routine being performed.

I.B. Actuation Assembly

As introduced above, the actuation assembly 110 may include a combination of one or more of: measurement sensors, for example end-effect sensors, vision sensors, and localization sensors. The actuation assembly 110 is configured to collect data related to the earth shaping vehicle 115 and environmental data surrounding the earth shaping vehicle 115. The controller 150 is configured to receive the data from the assembly 110 and carry out the instructions of the excavation routine provided by the computers 120 based on the recorded data. This includes control the drive system 210 to move the position of the tool based on the environmental data, a location of the earth shaping vehicle 115, and the excavation routine. The actuation assembly is further described with reference to FIG. 3.

I.C. On-Unit Computer

Data collected by the sensors 170 is communicated to the on-unit computer 120 a to assist in the design or carrying out of an earth shaping routine. Generally, earth shaping routines are sets of computer program instructions that, when executed control the various controllable inputs of the earth shaping vehicle 115 to carry out an excavation-related task. The controllable input of the earth shaping vehicle 115 may include the joystick controlling the drive system 210 and earth shaping tool and any directly-controllable articulable elements, or some controller 150 associated input to those controllable elements, such as an analog or electrical circuit that responds to joystick inputs.

Generally, excavation-related tasks and excavation routines are broadly defined to include any task that can be feasibly carried out by an excavation routine. Examples include, but are not limited to: site preparation routines, digging routines, fill estimate routines, volume check routines, dump routines, wall cutback routines, backfill/compaction routines. Examples of these routines are described further below. In addition to instructions, excavation routines include data characterizing the site and the amount and locations of earth to be excavated. Examples of such data include, but are not limited to, a digital file, sensor data, a digital terrain model, and one or more tool paths. Examples of such data are further described below.

The earth shaping vehicle 115 is designed to carry out the set of instructions of an excavation routine either entirely autonomously or semi-autonomously. Here, semi-autonomous refers to an earth shaping vehicle 115 that not only responds to the instructions but also to a manual operator. Manual operators of the earth shaping vehicle 115 may monitor the excavation routine from inside of the earth shaping vehicle 115 using the on-unit computer 120 a or remotely using an off-unit computer 120 b from outside of the earth shaping vehicle, on-site, or off-site. Manual operation may take the form of manual input to the joystick, for example. Sensor data is received by the on-unit computer 120 a and assists in carrying out those instructions, for example by modifying exactly what inputs are provided to the controller 150 in order to achieve the instructions to be accomplished as part of the excavation routine.

The on-unit computer 120 a may also exchange information with the off-unit computer 120 b and/or other earth shaping vehicles (not shown) connected through network 105. For example, an earth shaping vehicle 115 may communicate data recorded by one earth shaping vehicle 115 to a fleet of additional earth shaping vehicle 115 s that may be used at the same site. Similarly, through the network 105, the computers 120 may deliver data regarding a specific site to a central location from which the fleet of earth shaping vehicle 115 s are stored. This may involve the earth shaping vehicle 115 exchanging data with the off-unit computer, which in turn can initiate a process to generate the set of instructions for excavating the earth and to deliver the instructions to another earth shaping vehicle 115. Similarly, the earth shaping vehicle 115 may also receive data sent by other sensor assemblies 110 of other earth shaping vehicles 115 as communicated between computers 120 over network 105.

The on-unit computer 120 a may also process the data received from the sensor assembly 110. Processing generally takes sensor data that in a “raw” format may not be directly usable, and converts into a form that useful for another type of processing. For example, the on-unit computer 120 a may fuse data from the various sensors into a real-time scan of the ground surface of the site around the earth shaping vehicle 115. This may comprise fusing the point clouds of various spatial sensors 130, stitching images from multiple vision sensors 135, and registering images and point clouds relative to each other or relative to data regarding an external reference frame as provided by localization sensors 145 or other data. Processing may also include up sampling, down sampling, interpolation, filtering, smoothing, or other related techniques.

I.D. Off-Unit Computer

The off-unit computer 120 b includes a software architecture for supporting access and use of the earth shaping system 100 by many different earth shaping vehicles 115 through network 105, and thus at a high level can be generally characterized as a cloud-based system. Any operations or processing performed by the on-unit computer 120 a may also be performed similarly by the off-unit computer 120 b.

In some instances, the operation of the earth shaping vehicle 115 is monitored by a human operator. Human operators, when necessary, may halt or override the automated excavation process and manually operate the earth shaping vehicle 115 in response to observations made regarding the features or the properties of the site. Monitoring by a human operator may include remote oversight of the whole excavation routine or a portion of it. Human operation of the earth shaping vehicle 115 may also include manual control of the joysticks of the earth shaping vehicle 115 for portions of the excavation routine (i.e., preparation routine, digging routine, etc.). Additionally, when appropriate, human operators may override all or a part of the set of instructions and/or excavation routine carried out by the on-unit computer 120 a. Manual operation of the earth shaping vehicle 115 may be performed remotely via a gamepad, joystick, computer, mouse, or another input device.

I.E. General Computer Structure

The on-unit 120 a and off-unit 120 b computers may be generic or special purpose computers. A simplified example of the components of an example computer according to one embodiment is illustrated in FIG. 2.

FIG. 2 is a high-level block diagram illustrating physical components of an example off-unit computer 120 b from FIG. 1, according to one embodiment. Illustrated is a chipset 205 coupled to at least one processor 210. Coupled to the chipset 205 is volatile memory 215, a network adapter 220, an input/output (I/O) device(s) 225, and a storage device 230 representing a non-volatile memory. In one implementation, the functionality of the chipset 205 is provided by a memory controller 235 and an I/O controller 240. In another embodiment, the memory 215 is coupled directly to the processor 210 instead of the chipset 205. In some embodiments, memory 215 includes high-speed random access memory (RAM), such as DRAM, SRAM, DDR RAM or other random access solid state memory devices.

The storage device 230 is any non-transitory computer-readable storage medium, such as a hard drive, compact disk read-only memory (CD-ROM), DVD, or a solid-state memory device. The memory 215 holds instructions and data used by the processor 210. The I/O controller 240 is coupled to receive input from the machine controller 250 and the sensor assembly 210, as described in FIG. 1, and displays data using the I/O devices 245. The I/O device 245 may be a touch input surface (capacitive or otherwise), a mouse, track ball, or other type of pointing device, a keyboard, or another form of input device. The network adapter 220 couples the off-unit computer 120 b to the network 105.

As is known in the art, a computer 120 can have different and/or other components than those shown in FIG. 2. In addition, the computer 120 can lack certain illustrated components. In one embodiment, a computer 120 acting as server may lack a dedicated I/O device 245. Moreover, the storage device 230 can be local and/or remote from the computer 120 (such as embodied within a storage area network (SAN)), and, in one embodiment, the storage device 230 is not a CD-ROM device or a DVD device.

Generally, the exact physical components used in the on-unit 120 a and off-unit 120 b computers will vary. For example, the on-unit computer 120 a will be communicatively coupled to the controller 150 and sensor assembly 110 differently than the off-unit computer 120 b.

Typically, the on-unit computer 120 a will be a server class system that uses powerful processors, large memory, and faster network components compared to the on-unit computer 120 b because the on-unit computer 120 a controls individual sensors, for example vision sensors used for pedestrian detection, however this is not necessarily the case. Such a server computer typically has large secondary storage, for example, using a RAID (redundant array of independent disks) array and/or by establishing a relationship with an independent content delivery network (CDN) contracted to store, exchange and transmit data such as the asthma notifications contemplated above. Additionally, the computing system includes an operating system, for example, a UNIX operating system, LINUX operating system, or a WINDOWS operating system. The operating system manages the hardware and software resources of the off-unit computer 120 b and also provides various services, for example, process management, input/output of data, management of peripheral devices, and so on. The operating system provides various functions for managing files stored on a device, for example, creating a new file, moving or copying files, transferring files to a remote system, and so on. In some embodiments, data recorded and processed by components of earth shaping vehicle 115 and the actuation assembly 110 are stored on a cloud server.

As is known in the art, the computer 120 is adapted to execute computer program modules for providing functionality described herein. A module can be implemented in hardware, firmware, and/or software. In one embodiment, program modules are stored on the storage device 330, loaded into the memory 315, and executed by the processor 310.

I.F. Network

The network 105 represents the various wired and wireless communication pathways between the computers 120, the sensor assembly 110, and the earth shaping vehicle 115. Network 105 uses standard Internet communications technologies and/or protocols. Thus, the network 105 can include links using technologies such as Ethernet, IEEE 802.11, integrated services digital network (ISDN), asynchronous transfer mode (ATM), etc. Similarly, the networking protocols used on the network 150 can include the transmission control protocol/Internet protocol (TCP/IP), the hypertext transport protocol (HTTP), the simple mail transfer protocol (SMTP), the file transfer protocol (FTP), etc. The data exchanged over the network 105F can be represented using technologies and/or formats including the hypertext markup language (HTML), the extensible markup language (XML), etc. In addition, all or some links can be encrypted using conventional encryption technologies such as the secure sockets layer (SSL), Secure HTTP (HTTPS) and/or virtual private networks (VPNs). In another embodiment, the entities can use custom and/or dedicated data communications technologies instead of, or in addition to, the ones described above.

II. Electronic Actuation of an Earth Shaping Vehicle

II.A Sensor Data and Signal Processing

An earth shaping vehicle 115 is configured to navigate within a site to perform one or more earth shaping routines (or “excavation routines” hereinafter). For example, in implementations in which the earth shaping vehicle 115 is implemented to excavate earth from a site, the actuation assembly 110 adjusts an earth shaping tool between depths beneath the ground surface and depths above the ground surface in order to remove earth from the hole. The actuation assembly 110 may additionally instruct the chassis on which the earth shaping tool is mounted to navigate the vehicle 115 from the hole to a dump pile to deposit the excavated earth. In alternate embodiments, the actuation assembly 100 may actuate an earth shaping tool to remove obstacles within a site, for example by breaking the obstacle down so that the vehicle 115 can maneuver through the obstacle or adjusting earth within the site to remove the obstacle.

Although particular embodiments throughout the description are described with reference to an earth shaping vehicle or an excavation routine, a person having ordinary skill in the art would recognize that the described techniques, systems, and embodiments may also be applied to earth shaping routines involving any alternate earth shaping vehicle(s).

FIG. 3 is a diagram of the architecture for the actuation assembly 300, according to an embodiment. The actuation assembly 300 enables an earth shaping system to actuate an earth shaping tool mounted to an earth shaping vehicle as well as the earth shaping vehicle 115 in order to execute an excavation routine. The actuation assembly 300 is one embodiment of the actuation assembly 110. The architecture of the actuation assembly 300 comprises end-effector sensors 310, localization sensors 315, vision sensors 320, a safety system 325, and a controller 330. In embodiments in which the earth shaping vehicle is actuated using hydraulic components, the actuation assembly further comprises a hydraulic system 335 which includes a solenoid 340 and a valve 345. In other embodiments, the actuation assembly 300 may include more or fewer modules. Functionality, indicated as being performed by a particular module may be performed by other modules instead.

Communications performed wirelessly include, but are not limited to, 2.4/5 GHz Wi-Fi, cellular, LTE, Bluetooth, 900 MHz radio, or satellite communications. In one embodiment, end-effector sensors 310, localization sensors 315, and vision sensors 320 are mounted to the earth shaping vehicle 115 or the earth shaping tool 175 using existing fastening features on the earth shaping vehicle, for example threaded fasteners, such that the structure of the vehicle 115 need not be modified. In another embodiment, end-effector sensors 310, localization sensors 315, and vision sensors 320 are mounted to the earth shaping vehicle 115 or the earth shaping tool 175 by modifying the structure of the vehicle 115 or by designing a custom fastening feature by which the sensors may be mounted to the vehicle 115.

Although not shown, electronic components of the actuation assembly, and more generally of the earth shaping vehicle 115, may be powered by machine batteries or separate batteries provided by a manual operator. In some embodiments, an uninterruptible power supply may be used as a temporary backup system if the machine battery or separate battery fails or if the engine stalls during ignition. The action assembly 300 may implement power converters to convert voltages from the batteries to different electronic inputs. Power within the system may be distributed from a central bus bar or from multiple points and a switch may be used to direct power from the batteries to the electronics.

In one embodiment, the end-effector sensors 310 include at least one inertial measurement units or a similar sensor configured to couple to the machine base and each independent joint of the earth shaping tool. For example, an end-effector sensor is coupled at each joint at which the earth shaping tool experiences a change in angle relative to the ground surface, a change in height relative to the ground surface, or both. Based on recorded data, the end-effector sensors 310 produce a signal representative of a position and orientation of the corresponding joint relative to a site. The produced signal is processed by a controller 330 to determine the orientation and/or position of the earth shaping tool and the earth shaping vehicle 175. Data gathered by end-effector sensors 310 may also be used to determine derivatives of position information.

In one embodiment, the localization sensors 315 comprise at least one transmitter/receiver pair, one of which is mounted to the earth shaping vehicle and the other is positioned away from the vehicle 115, for example a GPS satellite. In implementations, in which a computer 120 determines a position of features or obstacles within a site relative to the position of the earth shaping vehicle 115, the localization sensors 315 comprise a single transmitter/receiver pair mounted to the earth shaping vehicle 115. Based on recorded data, the localization sensors 315 produce a signal representative of the position and orientation of the earth shaping vehicle 115 relative to the site which is processed by the controller 330.

The vision sensors 320 comprise a plurality of sensors configured to record a field of view in all directions in which the machine move. In one embodiment, the vision sensors 320 include LIDAR sensors, radar sensors, cameras, an alternative imaging sensor, or a combination thereof. The actuation assembly 300 may include a second set of vision sensors 320 configured to record the interaction of the earth shaping vehicle 115 with features within the environment, for example excavating earth from a hole, depositing earth at a dump pile, or navigating over a target tool path to excavate earth from a hole. Based on recorded data, the vision sensors 320 produce at least one signal describing one or more features of the site based on the position of the earth shaping vehicle 115 within the site, which is processed by the controller 330.

Under certain conditions, the safety system 325 is activated causing the earth shaping vehicle 115 to halt actuation of one or more components of the earth shaping vehicle 115. For example, sensor data collected by the vision sensors 320 may indicate that an obstacle obstructs a path over which the vehicle 115 is navigating, the safety system generates a signal instructing the earth shaping vehicle 115 to stop actuation of the drivetrain. Accordingly, the safety system 325 may comprise an emergency stop button that communicates with the vehicle 115 or the tool 175 using a wired connection, a wireless connection, or a combination of the two. A wired emergency stop button is connected directly the ignition of the earth shaping vehicle 115. In embodiments in which the emergency stop button is wired, the button can only be triggered by a manual operator, for example by pressing the button. In such embodiments, the wired button communicates based on an independent circuit or software from a wireless emergency stop button. Although described herein as potentially being a “button,” the emergency stop button may be designed as any other mechanism, for example a switch. Alternatively, the emergency stop button may be triggered without input from a human operator, but rather as an autonomous response to sensor data gathered by the end-effector sensors 310, localization sensors 315, vision sensors 320, or a combination thereof.

As described above, the controller 330 produces actuating signals to control the joints of the earth shaping tool to autonomously perform an earth shaping routine based on the signals produced by the end-effector sensors 310, localization sensors 315, and vision sensors 320. In some embodiments, while processing signals recorded by the sensors 310, 315, and 320 the controller 330 identifies one or more stop conditions, or conditions which would prevent the actuation of the earth shaping vehicle 115, which would trigger the safety system 325 to activate.

The actuating signals generated by the controller 330 may also be referred to as a target tool path, or a set of instructions which guide the earth shaping tool 175 to excavate a volume of earth as a part of an excavation routine, remove obstacles obstructed in the navigation of the earth shaping vehicle 115, release contents onto a dump pile, or some combination thereof. In some embodiments in which a target tool path is generated prior to deployment of the earth shaping vehicle 115 in the site, the controller 330 receives a previously generated target tool path.

Generally, a target tool path provides geographical steps and corresponding coordinates for the earth shaping vehicle 115 and/or earth shaping tool to traverse within a site, for example a route to circumvent an obstacle or a route between a hole and a dump pile. In addition, target tool paths describe actions performed by the earth shaping tool mounted to the earth shaping vehicle 115, for example adjustments in the position of the tool at different heights above the ground surface and depths below the ground surface. When the site is represented in the digital terrain model as a coordinate space, a target tool path includes a set of coordinates within the coordinate space. When a set of instructions call for the earth shaping vehicle 115 to adjust the tool mounted to the earth shaping vehicle 115 to excavate earth, dump earth, break down an obstacle, or execute another task the target tool path also includes a set of coordinates describing the height, position, and orientation of the tool within the coordinate space of the site 505. In some embodiments, multiple target tool paths may be implemented at different offsets from the finish tool path. For example, when excavating a hole with a graded excavation, multiple target tool paths may be implemented at different offsets.

Tool paths are defined based on several factors including, but not limited to, the composition of the soil, the properties of the tool being used to excavate the hole, the properties of the drive system 210 moving the tool, and the properties of the earth shaping vehicle 115. Example properties of the earth shaping tool 175 and earth shaping vehicle 115 include the size of the tool, the weight of the earth shaping tool, and the force exerted on the earth shaping tool 175 in contact with the ground surface of the site.

Some target tool paths achieve goals other than digging. For example, the last target tool path used at the conclusion of the excavation of the hole may be referred to as a finish tool path, which digs minimal to no volume and which is used merely to even the surface of the bottom of the dug hole. While moving through the finish tool path, the tool excavates less earth from the hole than in previous target tool paths by adjusting the depth of the leading edge or the angle of the tool beneath the ground surface. To conclude the digging routine, the earth shaping vehicle 115 adjusts a non-leading edge of the tool and reduces the speed of the drive.

As described above, the hydraulic system 335 comprises a solenoid 340 and a valve 345. In other embodiments, the hydraulic system 335 may include more or fewer modules. Functionality, indicated as being performed by a particular module may be performed by other modules instead. As described below, the controller 330 receives signals from a combination of the end-effectors sensors 310, localization sensors 315, and vision sensors 320. In some embodiments, the controller 330 is additionally coupled to a set of solenoids, each of which is further coupled to a corresponding hydraulic valve of the earth shaping tool. The controller 330 processes signals received from the sensors 310, 315, and 320 which instruct one or more solenoids to actuate a corresponding hydraulic valve, thereby navigating the earth shaping vehicle 115 or actuating the tool 175.

III. Precision Actuation of a Tractor

III.A Overview

Conventionally earth shaping vehicles are outfitted with two earth shaping tools—a first excavation tool mounted to a front side of the earth shaping vehicle and a second excavation tool mounted to a rear side of the earth shaping vehicle. In the particular case of tractors, the front excavation tool is a bladed excavation tool that may be actuated to move earth in a site by pushing large quantities of earth from a one location to another. Although such excavation tools may vary in structure and design, the excavation tools functionally similar in that they move earth from one location to a different location, for example by excavating earth from a site or by grading earth at a site. The rear excavation tool is an excavation tool that may be actuated to perform an alternate excavation routine or task than the front tool. In most cases, the rear excavation tool of a tractor is a ripper attachment, which may be lowered to penetrate the ground surface. FIG. 4A illustrates a tractor outfitted with a front earth shaping tool 410 and a rear ripper attachment 420, according to one embodiment. The ripper attachment 420 includes one or more ripper shanks, each of which is actuated to break through a ground surface. After lowering the ripper attachment 420 to penetrate the ground surface, the tractor 400 travels forward, for example over a target tool path, dragging the ripper attachment 420 through the ground surface. As the tractor 400 drags the ripper attachment 420 forward, the ripper attachment 420 may additionally break down rocks in the ground surface and other obstacles beneath the ground surface into rubble. The rubble may be removed from the site manually by an operator or by a different earth shaping vehicle 115. After removing the rubble, the surface of the site may be refined, for example by an earth shaping vehicle performing a routine to grade the ground surface.

During manual operation of the tractor 400, operation of the ripper attachment 420 is often obstructed from the operator's point of view, which results in imprecise movement and actuation of the ripper attachment 420. Accordingly, consistent with the description of FIG. 3, the ripper attachment 420 may be outfitted with end-effector sensors, for example end-effector sensors 310, mounted to the ripper attachment, the rear of the tractor 400, or both, to enable precise actuation of the ripper attachment even when the operator's view is obstructed. The end-effector sensors may detect variations in the ground surface, for example obstacles to be broken down into smaller pieces and, based on sensor data identifying the variations, the controller 150 may actuate the ripper attachment to penetrate the ground surface. In alternate embodiments, the controller 150 may actuate the ripper attachment to penetrate the ground surface at a deeper depth, for example to break obstacles deep beneath the ground surface.

However, excavation routines performed by a conventional ripper attachment mounted to the rear of a tractor typically result in unrefined, rough excavations of the ground surface. As described above, earth excavated by the ripper attachment is often displaced around the ground surface as smaller pieces of rubble. A conventional ripper attachment typically breaks down large obstacles or excavates large amounts of earth beneath the ground surface, but the conventional ripper attachment cannot be actuated to remove the smaller pieces of rubble from the ground surface. For example, the conventional ripper attachment could not be actuated to ground the ground surface within a margin of 0.1 feet.

As a result, the rear ripper attachment 420 of a tractor, or any other applicable earth shaping vehicle 115, may be replaced with a rear grading tool, for example a moldboard or a second bladed excavation tool resembling the front bladed tool, to enable to the tractor to perform excavation routines that require high precision or tighter tolerances. FIG. 4B illustrates a tractor outfitted with a rear grading tool 430 in place of a ripper attachment, according to one embodiment. In one embodiment, the rear grading tool 430 is a moldboard mounted to the rear side of an earth shaping vehicle, for example a tractor. In other embodiments, the rear grading tool 430 is an alternate bladed tool. The rear grading tool 430 is designed such that when a leading edge of the tool 430 is in contact with the ground surface, the leading edge is rigid enough to withstand the force exerted on the edges of the tool by the ground surface. The rear grading tool may also be retrofitted with end-effector sensors to enable automated actuation of the alternate rear excavation tool.

FIG. 5A illustrates an isometric view of a rear grading tool 500, which is an embodiment of the rear grading tool 430. The rear grading tool 500 comprises multiple attachment posts 510, where the rear grading tool 500 is coupled to an arm of an earth shaping vehicle 115. In the illustrated embodiment of FIG. 5A, the rear grading tool 500 includes three attachment posts 510. However, alternative embodiments of the rear grading tool 500 may include more or fewer attachment posts 510 depending on a combination of factors including, but not limited to, a size of the tool 500, a weight of the tool 500, a size of an arm of the earth shaping vehicle 115 where the tool couples, and a structure of the arm of the earth shaping vehicle 115. Each attachment post 510 may be constructed out of the same material(s) as the tool 500 or a different material(s) with structural properties more suitable for coupling the tool 500 to the vehicle 115 for an extended period of time. An attachment post 510 is coupled to an arm of an earth shaping vehicle 115 via any suitable coupling mechanism. In one embodiment, the attachment posts 510 are inserted into a ripper assembly on the rear of the vehicle 115. In conventional tractors, the ripper assembly on the rear of the vehicle 115 is used to secure the ripper attachment. The number of attachment posts in the rigid framework may depend on the number of ripper shanks previously coupled to the ripper assembly. For example, if a ripper assembly is configured to couple a ripper attachment with a single ripper, the rear grading tool 500 includes a single attachment post. The single attachment post couples to the ripper assembly in place of the ripper attachment.

In the illustrated embodiment of FIG. 5A, each attachment post 510 couples to a vehicle 115 via a bolt. Each attachment post 510 includes hole that complements a hole on either side of the ripper assembly. A single bolt is inserted through the holes of the ripper assembly and the complementary holes of the attachment posts to secure each attachment post to the rear of the vehicle 115. In alternative embodiments, multiple bolts may be used to secure the attachments posts to the ripper assembly. The ripper assembly may additionally include one or more hydraulic cylinders that are configured to actuate the rear grading tool and an arm of the vehicle during operation of an earth shaping vehicle 115.

The tool 500 may be designed using a single structure or a combination of structural elements permanently coupled together. In the illustrated embodiment of FIG. 5A, tool 500 includes a rigid framework that is constructed by fixedly connecting a upper piece 520 with a lower piece 530. In addition to the embodiments described herein, the rigid framework may be a single contiguous element. For example, the upper piece 520 and the lower piece 530 may be welded into a single structural element.

The upper piece 520 is designed to resemble a hollowed three-dimensional structure with an exposed top and front face. To couple each attachment post 510 to the tool 500, each post 510 is fitted into the angle formed by two perpendicular faces of the upper piece 520.

The lower piece 530 is a structural member coupled to the bottom face of the upper piece 520 at angle facing the ground surface (as illustrated in FIG. 5A). During actuation, the leading edge 535 of the lower piece 530 is the first edge of the tool 500 to make contact with the ground surface. The angle at which the lower piece 530 is oriented relative to the upper piece 520 may be determined based on the earth shaping routine being performed. For example, for an earth shaping routine where the tool 500 is actuated to make perpendicular cuts through the ground surface, the lower piece 530 is oriented perpendicular to the upper piece 520. As a second example, for an earth shaping routine where the tool 500 is actuated to grade a rocky surface, the lower piece 530 may be oriented at angle relative to the upper piece 520. As a third example, for an earth shaping routine where the tool 500 is actuated to grade a smoother surface, the lower piece 530 may be oriented at an angle relative to the upper piece 520 than the angle described in the second example. FIG. 5B illustrates a front view of the framework of the rear grading tool 500, according to an embodiment.

The curved surface of a rear grading tool is formed by coupling a curved member to the exposed side of the framework of the tool 500. As described herein, the curved member is a moldboard (e.g., the moldboard 540). However, in alternative embodiments, the curved member may be another suitable structural element. The moldboard coupled to the rigid framework is a curved metal blade configured to push material (e.g., snow and dirt) from a first location to a second location. The moldboard 540 is designed with a curvature that traces the orientation of the lower piece 530. The moldboard 540 may be designed with a height that extends from the leading edge 535 to the top edge of the upper piece 520. The moldboard 540 is secured to the lower piece 530 along the leading edge 535 and is secured along the side-facing edges of the upper piece 520. The length of the moldboard 540 may be greater than the length of the framework of the tool 500 in order to cover a greater area of the ground surface during excavation. The moldboard 540 may be constructed out of the same material(s) as the framework or a different material(s) with structural properties more suitable for withstanding the wear and tear of an earth shaping routine. In one embodiment, the framework of the tool 500 (e.g., the upper piece 520 and the lower piece 530) may be designed using steel, whereas the moldboard 450 is designed using an alternate metal. FIG. 5C illustrates a side view of a rear grading tool with a moldboard 540, according to an embodiment. The edge of the moldboard secured to the leading edge of the rigid framework is herein referred to as a cutting edge. During operation, the moldboard 540 is actuated such that the cutting edge of the moldboard engages with the ground surface to perform precise earth shaping routines (e.g., a grading routine).

In some embodiments, the rear grading tool 500 may be actuated three-dimensionally to adjust its pitch, yaw, and roll. In such embodiments, the arm of the earth shaping vehicle 115 to which the tool 500 is coupled may be modified, for example using a combination of actuation sensors, to enable three-dimensional movement of the arm of the earth shaping vehicle. The rear grading tool 500 may be coupled to an earth shaping vehicle via the rear attachment posts 510 such that the moldboard 540 pivots on an axis to control an orientation of the moldboard. Depending on specifications of the earth shaping routine being performed (e.g., a volume of earth being moved, a depth of the tool), the orientation of the moldboard may be adjusted by positioning a top edge of the moldboard ahead of or behind a bottom edge of the moldboard.

In some embodiments, the orientation of the lower piece 530 may be dynamically adjusted based on the earth shaping routine being performed. In such embodiments, the lower piece 530 is coupled to the upper piece 520 via one or more hinge mechanisms retrofitted with actuation sensors communicatively coupled to an operator device. Accordingly, an operator can generate and send instructions to adjust the orientation of the lower piece 530 depending on the earth shaping routine being performed. In such embodiments, the curved member 540 is designed out of a material that is flexible enough to conform to the varying angles of the lower piece, while also maintaining the structural integrity to perform various earth shaping routines.

III.B Operation of an Alternate Rear Excavation Tool

FIG. 6 is a diagram of the system architecture for the control logic 600 of an earth shaping vehicle 115, according to an embodiment. The control logic 600 is implemented by a software within a central computer, for example an on-unit computer 120 a or the off-unit computer 120 b, and is executed by providing inputs to the controller 150 to control the control inputs of the vehicle 115 such as the joystick. The system architecture of the control logic 600 comprises a navigation engine 610, a preparation engine 620, and an earth moving engine 630. In other embodiments, the control logic 600 may include more or fewer components. Functionality indicated as being performed by a particular engine may be performed by other engines instead.

The navigation engine 610 provides mapping and orientation instructions to the drivetrain of the earth shaping vehicle 115 to navigate the vehicle through the coordinate space of the site and along the target tool paths within the fill location. The preparation engine 620 creates and/or converts a digital file describing the target state of the site into a set of target tool paths. In combination, the set of target tool paths describes an earth moving routine and an organizational layout of a site along with any other instructions needed to carry out the earth moving (e.g., a location of earth to be moved, a location at which earth is to be filled, and a location of other vehicles relative to a primary vehicle). More information regarding the control logic and the generation of target tool paths by the preparation engine can be found in U.S. patent application Ser. No. 16/686,084, filed on Nov. 15, 2019, which is incorporated by reference herein in its entirety.

The earth moving engine 630 executes instructions (e.g., instructions encoded as a set of target tool paths) to actuate the front excavation tool 410, the rear grading tool 430, and the drive train to perform an earth shaping routine, for example an excavation routine to excavation from a location, a filling routine to fill earth at a location in a site, or a hauling routine to move earth from location to location in a site. In one embodiment, replacing the rear ripper attachment 420 with the rear grading tool 430 increases the overall earth moving capacity of the earth shaping vehicle. As the front excavation tool 410 pushes earth in a forward direction, the rear grading tool 430 is actuated to simultaneously pull earth in the same forward direction.

Additionally, because the rear ripper attachment 420 is replaced with a rear grading tool 430, the earth moving engine 630 executes instructions to lower an edge of the rear grading tool 430 to penetrate beneath the ground surface. Depending on the dimensions of the rear grading tool 430, the earth moving engine 630 may adjust the leading edge of the rear grading tool 430 to varying depths beneath the ground surface. When an operator controls a rear grading tool 430 manually, contact between the tool 430 and the ground surface is obstructed from the field of view of the operator. As a result, manual operation of the rear grading tool does not enable actuation of the tool at precise depths with tight tolerances. In comparison, automated or semi-automated actuation of the rear grading tool 430 enables more precise action of tool 430 with tighter tolerances by detecting contact between the tool and the ground surface and determining a precise position of the tool relative to the ground surface.

In one implementation, the earth moving engine 630 actuates the rear grading tool 430 to cut adjacent paths at different elevations to form a stepped excavation. First, the earth moving engine 630 adjusts a position of the leading edge of the rear grading tool to a first depth before excavating a first section, for example a lot, in the site. Second, the earth moving engine 630 adjusts the position of the leading edge of the rear grading tool to a second depth beneath the ground surface before excavating a section adjacent to the first section in the site. As an example, a site is divided into multiple adjacent sections. As an earth shaping 115 vehicle navigates through a first of the adjacent sections, the earth moving engine 630 actuates the rear grading tool to a first depth to excavate or grade the first section. As the earth shaping vehicle navigates forward to a second section of the site, the earth moving engine 630 actuates the rear grading tool to cut through the ground surface to a second depth to grade the second section at an elevation different from that of the first section. At each section of the site, the earth moving engine 630 actuates the rear grading tool to cut to various depths below the ground surface such that one or more sections are excavated at different elevations. In other embodiments, the earth moving engine 630 actuates the rear grading tool 430 to varying elevations to cut adjacent lots with steep drop-offs. In such an example, the earth moving engine 630 instructs the vehicle to back up to the shared edge of a lower lot before actuating the rear grading tool to make a cut while the earth shaping vehicle navigates forward.

In another implementation in which the rear ripper attachment 420 is replaced with a rear grading tool 430, the earth moving engine 630 positions an edge of the rear grading tool 430 at a depth in contact with the ground surface. In such an implementation, as the earth shaping vehicle navigates forward over a target tool path, the edge of the rear grading tool 430 in contact with the ground surface grades the ground surface. The earth shaping vehicle 630 may implement the rear grading tool 430 to grade the ground surface by the rear grading tool 430 to cover track marks of an earth shaping vehicle or to finely shape earth at the ground surface. Because at such a shallow depth, moving the tool forward requires less forward force than when the tool is lowered to a greater, digging-oriented depth, the rear grading tool 430 may be configured to hold a greater amount of earth beyond the standard mechanical and hydraulic constraints a tractor outfitted with a standard ripper blade.

In some embodiments, grading the ground surface may result in an uneven ground surface when the tool moves in a first direction, so the earth moving engine 630 may further actuate the rear grading tool 430 in a reverse direction. The earth moving engine 630 may additionally repeat the actuation of the rear grading tool 430 over a target tool path multiple times to achieve an even profile across the ground surface. Once the grading has been completed based on a set of target conditions specified by a target tool path, the earth moving engine 630 may repeat the grading process at various tool offsets to further excavate or grade areas of the site.

The earth moving engine 630 may additionally actuate the rear grading tool 430 to refine surfaces in the site. In some embodiments, navigation of an earth shaping vehicle 115 creates ruts or uneven surfaces where the chassis has navigated along the ground surface. In such embodiments, the earth moving engine 630 may actuate the tool 430 into contact with the ground surface to clean or remove such ruts and uneven surfaces. During an earth shaping routine, earth excavated by a front earth shaping tool accumulates in rows along the side edges of the front earth shaping tool. The rear grading tool 430 may be designed with a greater width than the front earth shaping tool, such that earth moving engine 630 can actuate the rear grading tool 430 to grade or smooth over the accumulated earth.

IV. Additional Considerations

It is to be understood that the figures and descriptions of the present disclosure have been simplified to illustrate elements that are relevant for a clear understanding of the present disclosure, while eliminating, for the purpose of clarity, many other elements found in a typical system. Those of ordinary skill in the art may recognize that other elements and/or steps are desirable and/or required in implementing the present disclosure. However, because such elements and steps are well known in the art, and because they do not facilitate a better understanding of the present disclosure, a discussion of such elements and steps is not provided herein. The disclosure herein is directed to all such variations and modifications to such elements and methods known to those skilled in the art.

Some portions of the above description describe the embodiments in terms of algorithms and symbolic representations of operations on information. These algorithmic descriptions and representations are commonly used by those skilled in the data processing arts to convey the substance of their work effectively to others skilled in the art. These operations, while described functionally, computationally, or logically, are understood to be implemented by computer programs or equivalent electrical circuits, microcode, or the like. Furthermore, it has also proven convenient at times, to refer to these arrangements of operations as modules, without loss of generality. The described operations and their associated modules may be embodied in software, firmware, hardware, or any combinations thereof.

As used herein any reference to “one embodiment” or “an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

While particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes and variations, which will be apparent to those skilled in the art, may be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims. 

What is claimed is:
 1. A tractor configured to move earth in a site, the tractor comprising: a chassis configured to drive the tractor through the site from a first location in the site to a second location in the site; a rear earth shaping tool coupled to a rear end of the tractor, the rear earth shaping tool configured to grade a ground surface between first location and the second location, wherein a set of sensors are coupled to the rear excavation tool and are configured to produce one or more signals representative of a position and an orientation of the rear tool relative to the ground surface of the site; and a controller communicatively coupled to the set of sensors and configured to produce actuating signals to actuate the rear excavation tool to grade the ground surface between the first location and the second location based on the one or more signals representative of the position and the orientation of the rear tool.
 2. The tractor of claim 1, wherein the rear earth shaping tool comprises a rigid framework and a curved member, the rigid framework configured to removably couple to the tractor and to support the curved member and the curved member configured to provide a surface of the rear earth shaping tool for grading the ground surface.
 3. The tractor of claim 2, wherein the rigid framework is coupled to the tractor by securing one or more attachment posts of the rigid framework to a ripper assembly of the tractor, the ripper assembly comprising one or more hydraulic cylinders configured to actuate the rear earth shaping tool.
 4. The tractor of claim 2, wherein the rigid framework comprises an upper piece and a lower piece with a leading edge oriented at angle towards the ground surface a, and wherein a surface of the curved member is curved along the orientation of the leading edge.
 5. The tractor of claim 4, wherein the curved member is secured to the leading edge of the lower piece and side edges of the upper piece.
 6. The tractor of claim 4, wherein the curved member is a moldboard with a leading edge configured to withstand a force exerted on the leading edge of the moldboard by the ground surface as the rear earth shaping tool grades the ground surface between the first location and the second location.
 7. The tractor of claim 1, wherein the tractor further comprises a front earth shaping tool coupled to a front end of the tractor, the front earth shaping tool configured to push earth in a forward direction from the first location to the second location and the rear earth shaping tool configured to pull earth on the ground surface in the forward direction from the first location to the second location.
 8. The tractor of claim 1, wherein the actuating signals comprise instructions to: adjust a leading edge of the rear earth shaping tool to a position in contact with the ground surface; navigate the chassis forward between the first location and the second location; and maintain the position of the leading edge of the rear earth shaping tool as the chassis navigates forward.
 9. The tractor of claim 1, wherein the actuating signals comprise instructions to: adjust a leading edge of the rear excavation tool to a first depth below the ground surface; navigate the chassis along a first path beginning at the first location while maintaining the leading edge at the first depth; navigate the chassis to a third location adjacent to the first location; adjust the leading edge of the rear excavation tool to a second depth below the ground surface, wherein the second depth is different than the first depth; and navigate the chassis along a second path beginning at the third location while maintaining the leading edge at the second depth.
 10. The tractor of claim 1, further comprising: a set of solenoids, wherein each solenoid is configured to actuate a corresponding hydraulic valve of the rear earth shaping tool to move the rear earth shaping tool towards the ground surface.
 11. An earth shaping vehicle (ESV) configured to move earth in a site, the ESV comprising: a chassis configured to drive the ESV through the site from a first location in the site to a second location in the site; a rear earth shaping tool coupled to a rear end of the ESV, the rear earth shaping tool configured to grade a ground surface between first location and the second location, wherein a set of sensors are coupled to the rear excavation tool and are configured to produce one or more signals representative of a position and an orientation of the rear tool relative to the ground surface of the site; and a controller communicatively coupled to the set of sensors and configured to produce actuating signals to actuate the rear excavation tool to grade the ground surface between the first location and the second location based on the one or more signals representative of the position and the orientation of the rear tool.
 12. The ESV of claim 11, wherein the rear earth shaping tool comprises a rigid framework and a curved member, the rigid framework configured to removably couple to the ESV and to support the curved member and the curved member configured to provide a surface of the rear earth shaping tool for grading the ground surface.
 13. The ESV of claim 12, wherein the rigid framework is coupled to the ESV by securing one or more attachment posts of the rigid framework to an assembly of the ESV comprising one or more hydraulic cylinders configured to actuate the rear earth shaping tool.
 14. The ESV of claim 12, wherein the rigid framework comprises an upper piece and a lower piece with a leading edge oriented at an angle towards the ground surface a and wherein a surface of the curved member is curved along the orientation of the leading edge.
 15. The ESV of claim 14, wherein the curved member is secured to the leading edge of the lower piece and side edges of the upper piece.
 16. The ESV of claim 14, wherein the curved member is a moldboard with a leading edge configured to withstand a force exerted on the leading edge of the moldboard by the ground surface as the rear earth shaping tool grades the ground surface between the first location and the second location.
 17. The ESV of claim 11, wherein the ESV further comprises a front earth shaping tool coupled to a front end of the tractor, the front earth shaping tool configured to push earth in a forward direction from the first location to the second location and the rear earth shaping tool configured to pull earth on the ground surface in the forward direction from the first location to the second location.
 18. The ESV of claim 11, wherein the actuating signals comprise instructions to: adjust a leading edge of the rear earth shaping tool to a position in contact with the ground surface; navigate the chassis forward between the first location and the second location; and maintain the position of the leading edge of the rear earth shaping tool as the chassis navigates forward.
 19. The ESV of claim 11, wherein the actuating signals comprise instructions to: adjust a leading edge of the rear excavation tool to a first depth below the ground surface; navigate the chassis along a first path beginning at the first location while maintaining the leading edge at the first depth; navigate the chassis to a third location adjacent to the first location; adjust the leading edge of the rear excavation tool to a second depth below the ground surface, wherein the second depth is different than the first depth; and navigate the chassis along a second path beginning at the third location while maintaining the leading edge at the second depth.
 20. The ESV of claim 7, further comprising: a set of solenoids, wherein each solenoid is configured to actuate a corresponding hydraulic valve of the rear earth shaping tool to move the rear earth shaping tool towards the ground surface. 